#include <stdio.h>
#include <assert.h>
void* my_memset(void* a, int b, size_t num)
{
	assert(a);
	void* ret = a;
	while (num--)
	{
		*(char*)a = b;
		a=(char*)a + 1;
	}
	return ret;
}

int main()
{
	char arr[] = "hello world";
	my_memset(arr, 'a', 5);
	printf("%s\n", arr);
	return 0;
}